Two-stage isomerization of normal paraffins



' reformingoperation.

' One' method refinersfor obtaining stocks ofhigher octane value in:Jvolvejs the 'isomeriaation Qf hc; to C 'n parafiinie hydro- Uni d St esPat f TWO-STAGE ISOMERIZATION OF NORMAL PARAFFINS Emmett H. Burk, Jr.,Hazelcrest, John Mooi, Homewood,

and Owen H. Thomas, Chicago, Ill., assignors to Sinclair RefiningCompany, New York, N.Y., a corporation of Maine No Drawing. Filed May 7,1959, Ser. No. 811,537 10 Claims. (Cl. 260-68366) This invention relatesto a hydrocarbon Conversion process and particularly pertains to atwo-stage process for isomerizing straight chain aliphatics to producebranch chain aliphatic structures, e,g. isomeric structures of n- Iparaffins, which are especially useful in providing gasoline componentsof high octane rating.

In recent years automobile manufacturers have steadily increased thecompression ratios of their spark-ignition engines as a means ofobtaining more power and greater efiiciency. As the compression ratiosof the engines in-i creases, the hydrocarbon fuel employed must be ofhigher octane rating to provide eflicient knock-free operationnotwithstanding that fuel octane rating can be increased through theaddition of tetraethyl lead, and other undesirable aspects of engineoperation, for instance pre-ignition, can be overcome by the use ofother additive components.. Thus the problem remainsfor petroleumrefiners to produce higher octane base hydrocarbon fuels undereconomically feasible conditions.

These refiners now have installed a substantial number of units forreforming straight run petroleum fractions in the presence of freehydrogen and over a platinum metal-alumina catalyst to obtain relativelyhigh octanev products. Primarilythese products, frequently calledreformates, are blended with other gasoline components such as thermaland catalytically cracked g'asolines, alky late, etc., and additivessuch as'tet'raethyl lead inobtaining present-day motor fuels. Thereformingoperation has a number of disadvantages. .First, as theoCtane'requirements of the blended engine fuels rise, the octane quality of thereformate must also "increase, if theblends be otherwise unaltered. Thisincrease results .in .a sub stantial reduction in yield particularly inobtaining reforrnates having. octanes RQN"neat) of the, order of 90 wasor above. ,When' 'thej severit'y' of the operation is increased,the-platinum metal-containing catalyst be comes fouled more o'ften withcarbonaceous deposits whichiequires more frequent,.regenerationsorreplace ments. The .platinum metalaalurn'ina catalysts; are 'relativelyexpensive, and either sreplacernentor withdraw! a1 fromuse duringregenerationmaterially increases-the, cost'of providing. a given volurnn,of freforrnate; These and other factorsfaffecting the yield-octane-.nuinberrcostrelationship make it'desirable for th'e'refiner to consider7 .variou's ways in. which high octane hydrocarbon fuel components canbe obtained" byjemploying proc essin 2,972,650 Patented Feb. 21, 1961.

ice

carbons, that is n-butane, n-pentane, n-hexane, n-heptane, n-octane,n-nonane and their mixtures with each other and with other hydrocarbonsin the same approximate boiling range. In general, as the side chainbranching of these n-parafiins increases, their octane ratings rise. A.number of catalysts are known as being useful in this type of operation.An example of such a system is that .described in US. Patent No.2,798,105 wherein a plati-r hum-alumina catalyst is employed toisomerize n-butane and n-pentane at temperatures upwards of 600 F. Atsuch temperatures the thermodynamic equilibrium between the feedstockand the isomeric product is such that conversion is unduly limited whichmeans that the product contains undersirably large amounts ofn-paraffins.

Due to the low octane rating of the n-paraffins .a given refiner may notbe able to blend the entire product from. they high temperatureisomerization system directly intov his gasolines. Rather, under presentcommercialconditions he will most likely be required to separate then-,.

and iso-paraffins in the product stream by distillation and then recycleall or a part of theuncoverted 'n-paraffins to the isomerizationreaction system It is, of course, immediately seen that the decreasedyield of isomer structures at the highreaction, temperatures isdisadvantageous, and in addition the provision of the requireddistillationfacilities materially adds to the cost" of octane.

enhancement. I e v e p In 'a process described in the copendingapplication of Keith and Burk, Serial No. 683,931, filed September 16,1957, C4 to C n-parafiinic-containing materials are isomerized atrelatively low temperatures while obtaining satisfactory conversion toisomeric structures. Thisiso merizing process includes contacting a C-to C n-pa raflin in the vapor phase with a noble metal-FriedelaCrafts'component-alumina catalyst at a't emperature. ofaboutv 1.150 to 450 F.,a space velocity in most cases of. about.

' directly in a gasoline poolwithout requiring distillation 0.5 to l0:lweights ofn-paraffin perweight ofcatalyst per hour (WI-ISV) -in thepresence of free hydrogen and whileproviding about 0.0516 35 ofa-hydrogen halide I based on the n-paraffini When followingthis'procedure the amount of isomer structures in the product are sufiicient such that-the overall product stream -can-be used foruseparatingthe n-paraffins from-the product. fflhe feeds employed in this process.are usually pretreated to l lower the amount of l'aromatic naphtheneint-, .;purit ies: contained thereinjsince the impurities can; have toprovide appreciable isomerization" of'th'e n-parafiins to enhance theoctane. rating of-theifee'd, e.g-.' above about;

"methods other than; the platinum metal-alurninagcatalyst ow; underconsideration by petroleuni 94, and at the sameftimeprovidinghydrogenationfofthe; aromatics. The product 'frornthe-firststageisfurther; enhanced in octane rating in thesecond stage at -lesssever e temperature conditions: than those employed, in the i I firstStage. andiising equivalent or greaterspace velocities:

for Qa I giVen entagon: of n-paraflin to isoparaffin than theabove-mentioned copending application, Serial No. 683,931. In otherwords, due to the. use of our initial conversion zone the second stageof this invention can provide greater amounts of high octane productfrom a feedstock containing aromatic poisons for the second stagecatalyst than would be obtained by employing the second stage alone. Atset forth in the above copending application, hydrogen halide isadvantageously included in the hydrogen recycle gases employed in thisprocess. Accordingly, another advantageous feature of our two-stageprocedure is the simplicity and the interdependent relationship betweenthe two stages allowing use or": common hydrogenrecycle gases containinghydrogen halide in each stage since the catalyst employed in the firststage is stable in the presence of hydrogen halide.

In the first stage (stage I) of the present process, which can beconducted in the presence of hydrogen recycle gases containing hydrogenhalide at atomic weight between 35 and 85, some isomerization of C to Cn-paraffins is effected along with the hydrogenation of aromatics, e,g.benzene and toluene. Benzene, when present in substantial amounts, isconverted to methyl cyclo pentane and cyclo hexane which are tolerablein the first stage and are tolerable in the second stage in amounts lessthan about 12' weight percent based upon the hydrocarbon feed. Whenlarge amounts of naphthenes are present in the feed, for instance, inamounts above about 12 and up to about or weight percent, temperaturesfrom about 575 F. to650 F. can be provided in the first stage to reducethe naphthene content of the feed to less than about 12 weight percentand preferably less than about 10 weight percent, eg about 1 to 9wcightpercent, by selectively cracking the naphthenes to, for instance,isoparafiins and other products, while effecting some isomerization of Cto C n-paraffins along with the hydrogenation of aromatics. Theselectivity to C and higher products for the isomerization of n-pentanein the first stage is generally up to about 94 volume percent or more..The product of the first stage or any portion thereof is charged to thesecond stage (stage II) which isv char acterized by good selectivity,for instance generally above about 97% and frequently above about 98%,for the isomerization of normal pentane to iso-pentane.

In the initial stage of the process of the present inven tion, C to Cn-paraffinic materials in the hydrocarbon regenerable, exhibits goodactivity as well as good aging characteristics and is stable in thepresence of hydrogen halide employed in the second stage of the process.Another highly advantageous feature provided by the use Angstrom unitssize. Of the noble metals platinum, palladium and rhodium are preferred.

The boria component is surface dispersible on the support and seemsessentially inert to hydrogen halide. It is employed in amountssufficient to enhance the life of the alumina support and such amountsare, therefore, preferably added in direct proportion to the area of thesupport. For instance, the amount of boria will usually be about 3 or 5to 20 weight percent and preferably about 8 to 15 Weight percent of thecatalyst. These amounts are particularly effective on alumina havingsurface areas of about 350 to 550 square meters per gram (BET) beforeuse.

in order for the catalyst to maintain its activity for long periods oftime when isomerizing the C to C n-parafiins, it is highly desirable toprovide a hydrogen halide of atomic weight between and 85, e.g. HCl, HBrand their mixtures, in the-reaction zone. The hydrogen halide can beadded along with or in the n-paraflin feed and preferably in hydrogenrecycle gases employable in either stage of the present process. Thehydrogen halide is provided in an amount of at least about 1 up to about25 percent, based on the hydrocarbon feed, preferably at least about 1%up to about 20% and advantageously about 5 to 15 weight percent ofhydrogen halide or hydrogen halide of a hydrogen halide-producingmaterial based on the hydrocarbon feed. The addition of the hydrogenhalide in these concentrations is continued over the processing periodin order to maintain an adequate concentration of this component andinsure the stability of the catalyst against undue aging. The hydrogenhalide can be added separately to the reaction zone, in thehydrogencontaining recycle gases, or in the n-paraifin feedstock.

Instead of supplying the hydrogen halide with an atomic weight between35 and 85 as such, an organo-halogen compound or other substance whichwill produce the hydrogen halide under the isomerization conditions canbe employed; Suitable hydrogen halide precursors of this 1 type includethe elemental halogens, chlorine,brornine and fluorine; monoandpolyhalo-alkanes such as carbon tetrachloride, chloroform and tertiarybutyl chloride; or.

other available materials which-will be converted under the conditionsof isomerization to provide the hydrogen halide.

The noble metal and boria constituents of the catalyst are deposited onan absorptive alumina base of the acti'- vated or calcined type. Thealumina base is usually the major component of the catalyst, generallyconstituting at least about 75. weight percent on the basis of thecataof this catalyst in the initial stage lay in the lowering of a thearomatic and, when present in amounts aboveabout 12 weight percent andunder favorable temperature conditions, naphthene ingredients containedin the feed since the catalyst has a relatively high tolerance limit forthese 'as well as other ingredients.

7 Thus, for instance, feeds containing up to about 0.004 or more percentsulfur, up to about 10 percent aromatics and up to about 20 percentnaphthenes canbe'tolerated';

*The catalyst employed in the initial stage of the present lyst andpreferably at least about to percent; The

catalyst'b'ase is an activated or gamma-alumina such as' thosefderived'by calcination of amorphous hydrous alumina, aluminamonohydrate, alumina trihydrate orjtheir mixtures The catalyst baseprecursor most adyarita geously is amixture predominating in, orcontaining a' major proportion of, forinstance about 65 to weightpercent, one or more of the alumina trihydrates bayerit e. L

bayeriteflllrandomitel or gibbsite, and about 5' to 35 weight percent ofalumina monohydrate (boebm'ite), amorphous hydrous alumina ortheirimixture. The alu-j,

mina base can contain small amounts of other solidoriprocess includescatalytically efiective amounts of a noble;

or platinum group metal and boria supported on an alu mina base.

The catalyst generally contains about 0.01 to .2 weightpercent,preferably 0.1 to 1 weight percent, ofone or more of'theplatinum metals of group Vlll,

that is platinum, palladium, rhodium,- ruthenium, osmium' or iridium.The small amount of noble 'metal rnay be present in the metallic form oras a sulfide, oxide or other" combinedform. The metal may interact withother constituents of the catalyst, but if during usethe noblemetal bep'resentiin metallic form, then it is preferred that it be so finelydivided that it is not detectable'by X -ray diffrae-c tioumeans, i.e.that it "exists as crystals ofless'th'an 50 ides sucha's silica,magnesia, natural or activated clays (such kaolinite, montmorillonite,halloysite, 'etc.). .titania, zirconia, etc'., 'or theirlmix'tures.Although the components of the catalyst 'can'vary as stated, the pre}ferred catalyst contains platinum and "boria deposited on activatedalumina;

The f rst stage reaction conditions the method of the present inventioninclude a temperature sufficient to maintain the n-parafiin feed thevapor phase under the pressure employed; Generally, this temperatureyilf moving or fluidized bed or'in any otherconvenient type of handlingsystem. The fixed bed system seems. most advantageous at thistime andthe space velocity will in most cases be from about 0.5 to 20:1,preferably about 0.75 to :1, weights of n-paratfin per weight ofcatalyst per hour (WHSV). a.

Free or molecular hydrogen must be present in our first stage reactionsystem and the hydrogen to n-parafi'in molar ratio will usually be fromabout 0.01 to :1 or more, preferably about 2 or 3 to 10:1. Conveniently,the hydrogen concentration is maintained by recycling hydrogen-richgases from the reaction zones of either the first or second stages.These gases contain hydrogen halide at least after the initialprocessing period and as there is usually no substantial consumption ofthe halide after this period the desired concentration in the feed canbe maintained for use in the second reaction zone merely by recyclingthe hydrogen halide-containing gases, for instance, with a hydrogenhalide concentration on the order set forth above. As previously statedthe preferred catalyst base material is an activated or gamma-aluminamade by calcining a precursor predominating in alumina tribydrate. Analumina of this type is disclosed in US. Patent No. 2,838,444. Thealumina base is derived from a precursor alumina hydrate compositioncontaining about 65 to 95 weight percent of one or more of the aluminatrihydrate forms gibbsite, bayerite I and bayerite II (randomite) asdefined by X-ray diffraction analysis. The substantial balance of thehydrate is amorphous hydrous or monohydrate alumina. Trihydrates arepresent as well-defined crystallites, that is, they are crystallineinform when The crystallite examined by X-ray diffraction means!- sizeof the precursor alumina tribydrate is relatively large and usually isin the 100 to 1000 Angstrom'unitv range. The calcined alumina has alarge portion of its pore volume in the pore size range of about 100 to1000 Aug strom units generally having about 0.1 to about 0.5 andpreferably about 0.15 to about 0.3 cc./ g. of pore volume in this range.As described in these applications the calcined catalyst base can becharacterized by large surface area ranging from about 350 to about 550or more state has substantially no pores of radius less than 10 Angstromunits andthe surface area of the catalyst isless than 350 square meters/gram and most advantageously is in the range of about 150 to 300 gram'.

metal, by impregnation from a hot, heated or boiling solution of water.after it has been formed by tableting or extrusion and calcined. Afterthe boria is added according to this procedure, the catalyst can berecalcined.

The catalyst of the initial stage of the present invention can be easilyregenerated employing conventional procedures, for instance bysubjecting it to an oxygencontaining gas at temperatures sufiicient toburn off carbon deposited on the catalyst during the conversion ofpetroleum hydrocarbon feedstock. This oxygen-contain ing gas, e.g. anoxygen-nitrogen mixture, can contain about 0.01 weight percent to 5weight percent oxygen but preferably contains about 0.5 to 1.5 weightpercent oxygen and is introduced at a flow rate such that the maximumtemperature at the site of the combustion is below about 1000 F.

In the second stage of the present process, the product from the firststage is treated with a solid catalyst which is useful in theisomerization of the C to C n-paraflins in the presence of free hydrogenand at relatively low temperatures to afford highly satisfactory yieldsof isomer products. This catalyst, when employed under properconditions, has an excellent stability against aging. Due to the high,isomer content of the resulting product from the second stage, a givenrefiner may find that it can be blended directly into his gasolineswhich avoids the necessity for providing distillation facilities toseparate the unconverted n-parafiins. However, even if such facilitiesneed to be provided inorder to obtain products more concentrated inisomeric structures the catalyst of the second'stage still providesincreased conversion to as compared with others previously icallyeffective amounts of a noble or platinum group metahan aluminum halideFriedel-Crafts component and .at least ultimately in the reaction zone,a hydrogen halide metals offgroup VIII, that is platinum, palladium,rhodium, ruthenium, 'osmium or iridium. The small amount 'of" noblemetal may be present in the metallic form or as a sulfide, oxideorother'combined form.

. The metal may interact with otherconstituents ofthe square meters/-The platinum group metal, e.g.' platinum; component ofthe catalyst canbeadded t olth e alumin'a base'byknown procedures. For instance, theplatinum metal; component can be deposited on a.calcinedjloractivatedalumina, but it is preferred to add -theplatinummetal 'ly 1s about- 2 to, 50 we1ght percent, preferably about .10 to. 30weight percent-,of the catalyst andthis componentcomponent to thealumina-hydrate base precursor. Thus 7 platinum can'be addedthroughreaction ofafhalogen platinum-acid,- for instance, fluoro-,,ichloro-Qbromoor" iodo-platinic acid, and hydrogen sulfide inxan aqueousslurry .of' the alumina hydrate. Thehydrogen sulfide can be employed asa gas or an aqueous solution. Alternatively the platinum component{canbeprovided-by mixing an aqueous platinum' sufide sol with thealumina,

hydrate. ,This sol canbe; made by reac't'ionffin anja quegfous medium ofa halogen platinicacid' with hydrogem, sulfide. I The alumina hydratecontaining" "the platinum.

metal can be dried-and calcinedusually at a temperature activatedorlgamma alumina modifications. The, boria.

it'spfeparation. -It-j mayv be" incorpo ponent.

ucatalyst, but if during use the noble metal be present in metallic formthen it is preferred that it be so finely divided that it is notdetectable by X-ray diffraction means, i.e. that it existsas crystals ofless than" 50 Augstrom units sizen p fer g q. a I

The aluminum halide Friedel-Crafts-cornponent usual 'can'be, forinstance, AlCl AlBr "and-similar metal halideswhere one or more 'Of the.anions are replaced. with. another anion such as hydroxide. Mixtures'ofthese, i. Friedel-Crafts,components can also be usedf'aluminum' chlorideis, however, thepreferred Friedel-Crafts. com-. i

A hydrogenhalide of atomic 'weight between35 and is p'rovided'in thereaction zone of' theseeorid stage I in order for the catalysttomaintain the activity of th- "catalystffoi long' periods of time whenisomerizing the C to C n-paraffins from the firststage The amounts,mannerfof employment and types of hydrogen halide pro: I vided in' thesecond stageare essentia lly'fthe. same as in the firststagedescribedabove. .Thus we have found that the catalyst shouldcontain about 0.5 to15%;or

V nioreof the hydrogen halide. The hydrogen jhalide's of atomicweight-between35 and 85 ,includegifor, instance, mn ee e d tfl mes-"mama It is frequently added to the catalyst -Of the noble metals,platinum.-is

' 0.5 to; 105i weights of'mparailin tures'a'nd preferably the amount ofthis component on the-alumina baseis less than about of the catalyst.Usually this halide will be added to the catalyst after it is placed inthe isomerization reaction. Conveniently this can be done by includingin the charge stock from the initial stage about 1 to 01 weight percent,advantageously about 5 to 15 weight percent of the hydrogenhalide or ofa hydrogenhalldoproducing material. The addition of the hydrogen halidein these concentrations based on the n-parafiin in the second stage, asin the case of the first stage, is continued over the processing periodin order to maintain an adequate concentration of this component on thealumina base and insure the stability of the catalyst against undueaging. The hydrogen halide can be added separately to the reactionsystem, in the hydrogen-containing recycle gases or in the charge stockfrom the initial stage. Also the hydrogen halide might be added to thecatalyst before charging it to the reactor.

instead of supplying the hydrogen halide of atomic Weight between and 85as such, an organo-halogen compound or other substance which willproduce the hydrogen halide under the isomerization conditions can beemployed. Suitable hydrogen halide precursors include the elementalhalogens, chlorine and bromine; monoand polyhalo-alltanes such as carbontetrachloride, chloroform and tertiary butyl chloride; or otheravailable materials which will be converted underthe'conditions ofisomerization' to obtain the hydrogen halide. Most advantageously about5 to 15 weight percent of hydrogen chloride is employed as the hydrogenhalide on the catalyst and is supplied during the processing period.

The noble metal, Friedel-Crafts and hydrogen halide, of atomic weightbetween 35 and 85, constituents of the catalyst are deposited on anabsorptive aluminahase of the activated or calcined type, as describedin connection with the catalyst employedin the first stage. The base isusually the major component of the catalyst, constituting about 40 to 88or 98 weight percent, preferably at least about The catalyst base is anactivated or gamma alumina such as those derived by calcination ofamorphous hydrous alumina, alumina monohydrate, alumina trihydrate ortheir mixtures, for instance as in the catalyst of our first stagereaction zone. The catalyst boria, natural or-activated clays (such askaoliuite, montmorillonite, halloysite, etc.), titania, zirconiap etc.,for their mixtures. Although the components ofthe catalyst can vary asstated, the preferred catalyst contains platinunnaluminu'm chloride andhydrogen chlo zde; deposited on activated alumina.

The isomerization reaction conditions used. the second'stage otlthemethod Of::l .h present invention. include a temperature sufificient tomaintain the ri -paraffin feed in zthevapor phase'under the pressureemployed. General- I ly, .this.temperature.will be from about 150 to 450F preferably about 250 to 400 5., while the pressure Will besuperatmospheric ranging fromabout 50 to 1000 to n-paraffin molar ratiowill usually be from about 0.01

These gases contain hydrogen halide at least after the initialprocessing period and as there is usually no substantial consumptionofthe halide afterthis period the desired concentration in the feed can bemaintained merely by recycling the hydrogen gases containing hydrogenhalide of atomic weight between 35 and 85 since, for instance, thehydrogen halide concentration can with advantage be about 0.5 to 35weight percent of the recycled gases.

A convenient manner in which the catalyst of the sec end stage of thepresent invention can be prepared is to add the Friedel-Crafts componentto the base containing.

the platinum metal component. It is highly desirable to keep thecatalyst protected from moisture to avoid hyrolysis and the resultingloss of aluminum halide from the catalyst. Thus it is most advantageousto employ this catalyst under essentially anhydrous conditions includingthe provision of the hydrogen halide in anhydrous form. Duringregeneration of the catalyst to remove carbonaceous deposits by burningin an oxygen-containing gas, some aluminum halde may be lost. Thus, itmay be necessary to add additional amounts of this halide as bysublimation before continuing the isomerization.

Even though the catalysts used in each of the first and second stagescan be employed directly in the isomerization system, it is preferredthat they be pretreated with free or molecular hydrogen or a mixture ofhydrogen and hydrogen halide. For instance, the catalyst used in thefirst stage can be pro-reduced or preactivated by treatment withhydrogen at an elevated temperature, for instance about800 to 1000" F.The catalyst used in the second stage can be heated to about 650 F. in aslowly flowing stream of hydrogen or hydrogen-hydrogen chloride mixturefor a period of time sufiicient to activate the catalyst. It may bedesirableto employ lower temperatures in the pretreatment of the secondstage catalystto avoid undue loss of aluminum halide by sublimation eventhough this may decrease the rate of activation. After the activationthe pressure can be increased as desired and the product from the firststage is charged to the reaction system. Generally, the activity of thecatalyst hydrogen halidesupported on the alumina base.

p.'s.i.'g., preferably about 200 to- 600 p.s.i.g. The. catalyst can beused as a fixed, moving or fluidized bed or in any other convenient'typeof handling system. The

fixed bed system s'eemsmost. advantageous at this tim e and the spacevelocity will in niost cases be from about per Weight of catalyst perhour-(WHSV). p free or molecular hydrogen 'must' alsobe present in l sse o s t st ut ca i sy tem-r the h dro en Eriedel-Crafts component. I

-As previously- -stated the preferred catalyst base terial isanactivated or gamma-alumina made by ,cal-

cining'a precursor predominating in alumina trihydrate as exemplified-inU.S .Patents 2,838,444 and 2,838,445. The platinum metal component ofourjcatalys'ts can be added to the alu'minaflbase. by l nown proceduresdeponent-to thehigh areacatalyst baseof US. Patent .No.

2,838,444 hasbeenfound to decrease the surface area,

for instance-frequently in proportion to the amount of Friedel-Craftscomponent added. Use of the catalyst in the isomerization system orhydrogenpretreatment seems to tend to increase the area apparentlythrough loss ofthe The following specific example will 7 p servetoillustrate the-inventiontbut'it isnot to beTconsidered limiting? I I 9EXAMPLE I A noble metal-alumina composition of the kind described in U.S. Patent No. 2,838,444, can beremployed in preparing the catalyst usedin the process of our invention. The composition of this application canbe made as follows. Pure aluminum metal is dissolved in purehydrochloric acid, and the resulting solution is mixed with deionizedwater to form an aqueous aluminum chloride solution and an alumina gelis prepared equivalent to approximately 65 grams of A1 per liter. Aseparate deionized water solution of NH OH is prepared containingapproximately 65 grams of ammonia per liter. These two reagents inapproximate volume ratio of 1:1 are intimately mixed as a flowing streamat a pH of'8.0. The flowing stream is passed to a stoneware containerand an alumina hydrate is visible. The precipitated hydrate is filteredfrom the mother liquid and washed to 0.2% chloride by successivefiltrations and reslurryings in deionized water until the desiredchloride concentration is reached. In each reslurrying ammonia is addedto give a pH of about 9. The washed hydrate is. covered with water in acontainer and aged at about 90 F. until it is approximately 70%trihydrate, the remaining being substantially of the amorphousorfmonohydrate forms. The total hydrate compositon is comprised of 42%bayerite, 18% randomite, 11% gibbsite, 20% boehmite, and 9% amorphous asdetermined by X-ray diffraction, analysis. The aged hydrate is mixedwith deionized water in a rubber lined container to provide a slurry ofabout 7 weight percent A1 0 at a pH of about 8.0. A chloroplatinic acidsolution in deionized Water (0.102 gram platinum per milliliter) isstirred into the slurry and the slurry is then contacted with adeionized water solution which has been saturated with H at 78 F. to precipitate the platinum. The pH of the slurry is adjusted to 6.0 to 6.5 byammonium hydroxide addition and the solids of the slurry are dried on ahorizontal drum drier to give a powder of' generally less than 20 mesh.The drum dried powder is mixed in a, planetary type dough beater withsufiicient deionized water to indicate 26 weight percent water on aCentral Scientific Company Infra-Red Moisture Meter containing a 125watt bulb, Cat. No 26675. The resulting mixture is forced through a dieplate having holes in diameter bolted to a 3 /2" welding engineers screwextruder. The resulting strands are broken to particles of lengthvarying generally etween about to 1 The particles 'are dried aty230 F.and calcinedrby heating to 925 F. in a flow of nitrogen gas followedbya'flow of air while the composition is maintained at a temperature inthe range of 865 F.to 920 F. [The composition thus produced analyzesabout 0.6'fweight percent of platinum-which is in sufficiently dividedform so as to exhibit by X-ray diffraction studies the substantialabsence of crystallites. or crystals of size larger than 50Angstromunits After the calcination'the composition has an area (BETmethod) within the range from about to 550 square meters/gram. A

(B) Preparation of noble metal-boriaflrluntind catalyst Aplatinum-alumina composition prepared essentially A at 140 C., for 4hours. The catalyst was stirred occa-' sionally while drying. The ovendried catalyst was transferred to a sagger and placed in a mufflefurnace preheated to 1000" F. The catalyst was held at1000- for 2 hoursand cooled in a desiccator. Analysis: 9.95% B 0 7 An example ofpre-activation follows: 40 grams of this catalyst were supported onglass beads in the center of a 1-inch I. D.v Universal Stainless SteelReactor. The

;reactor was s'etLin place in a bronze-block furnace controlled byMicroswitch thermostats. The catalyst was heated to--800- -'F. underatmospheric pressure of pure hydrogen flowing at about 2 cu. ft./hr.These conditions were. maintained for'lohours. At this time the reactoris cooled to operating temperatures and reaction conditions areestablished for processing the parafiin feed.

(C) Preparation of noble metal-aluminum halide-alumina catalyst Aplatinum-alumina catalyst prepared essentially as described above inExample I(A), except that air was used for the complete calcinationprocedure and containing about 0.6 percent platinum was employed in theprocess of the present invention by the following procedure. Aone-liter, three-necked flask was fitted with a heating mantle,thermometer and an air inlet line having a drying tower filled withDrierite. The flask was fastened to .a Syntron Paper Jogger whichprovided agitation of the catalyst during the impregnation. The flaskwas swept out with dry air for about 10 minutes. 150 grams of theplatinum-alumina catalyst and 45 grams of aluminum chloride were chargedto the flask.- The air I (D) The two stage process 7 V 1 ANALYSIS onnnnnstroon Feed (wt. percent) 3 i-C 4 i-C 0. 1:1-(:5 V 2.2 dimethylbenzene 2,3 dimethyl benzene+2 methyl pentane .z... 3 methyl pentane11-C6 V i MCP Benzene i-C i-C The'present inventionv is illustrated byRun A, presented below in Table I,,which was conducted under theconditions specified above for the two-stage process of the presentinvention. The results are also presented in this table. The catalystemployed in stage I was prepared by essentially the same procedure setforth in Example I(B) above except that the catalyst comprised 0.6

TABLE I Run A Stage I Stage II Feed Samev feed analyzed i Product E-.am' le 1 from StageI Condition:

Wt. percent H01 based on feed 12. 5 12. 5 Pressure, p s is 500 500 625300 V 3 2 5. 6' 5. 6 Product:

54. 0 64. 6 75. 2 86. 0 2, 2 D 7. 2 20. 8 Selectivity C5 97. 2 99. 3

It is claimed: 1. In a method for isomerizing C to C n-paraflins in afeed containing aromatics, the steps comprising contacting saidn-parafiins under first stage conditions with a first stage catalyst ata temperature of about 200 to 750 F. and in the presence of freehydrogen to produce 'a first stage reaction product, contacting thefirst stage reaction product under second stage conditions with a secondstage catalyst at a temperature from about 150 'to 450 F. and in thepresence of free hydrogen and while providing about 1 to 25 percentof ahydrogen halide with an atomic weight between 35 and 85 based on thefirst stage reaction product; said first stage catalyst consistingessentially of about 0.01 to 2% of a platinum group noble metal andabout 3' to of boria on activated alumina and said second stage catalystconsisting essentially of about 0.01 to 2% of a platinum group noblemetal and about 2 to 50% of an aluminum halide Friedel-Crafts componenton activated alumina.

2. In a method for isomerizing C to C n -paraifins in a feed containingaromatics, the steps comprising contacting said n-parafiins under firststage conditions with .a first-stage catalyst at a temperature of about200 to 750 F. and in the presence of free hydrogen while providing about1 to percent, based on the feed, of

jaydrogen halide with an atomic weight between '35 and 85 to produce afirst stage reaction product, contacting on the first stage reactionproduct; said first stage catalyst consisting essentially of about 0.01to 2 percent of a.

platinumgroup noble metal and about.5 to 20 percent of boria onactivated alumina and said second stage catalyst consisting essentiallyof about 0.01 to 2. percent of a platinum group noble metal and about 2to 50 percent of an aluminum halide Friedel-Crafts component onactivated alumina.

3. In the method of claim 2 wherein the platinum 52 group noble metal ofthe second stage catalyst is platinum.

4. In a method of claim 3 wherein the first stage temperature conditionsare from about 500 to 650 F.

5. In a method for isomerizing C to C n-parafiins in a feed containingaromatics, the steps comprising contacting said n-parafiins under firststage conditions with a first stage catalyst at temperatures of about500 to 650 F., superatmospheric pressure, and the presence of freehydrogen while providing about 1 to 25%, based on the feed, of hydrogenhalide with an atomic weight between 35 and to produce a first stagereaction product of enhanced octane rating and containing hydrogenatedaromatics, and contacting the first stage reaction product under lesssevere second stage conditions, to further enhance the octane rating ofthe first stage reaction product, with a second stage catalyst attemperatures from about 250 to 400 F, in the presence of free hydrogenand while providing about 1 to 25% of a hydrogen halide with an atomicWeight between 35 and 85, based on the first stage reaction product;said first stage catalyst consisting essentially of about 0.01 to 2% ofa platinum group noble metal and about 5 to 20% of boria on activatedalumina and said second stage catalyst consisting essentially of about0.01 to 2% of a platinum group noble metal and about 2 to 50% of analuminum halide Friedel-Crafts component on activated alumina.

6. The method of claim 5 wherein the first stage catalyst consistsessentially of about 0.1 to 1 weight percent of a platinum group noblemetal and about 8 to 15 weight percent of boria on activated alumina andthe second stage catalyst consists essentially of about 0.1 to 0.75weight percent of a platinum group noble metal and about 10 to 30 weightpercent of an aluminum halide Iriedel-Crafts component on activatedalumina.

7. The method of claim 5 wherein the first stage catalyst consistsessentially of about 0.1 to 1 weight percent of platinum and about 8 to15 weight percent of boria on activated alumina and the second stagecatalyst consists essentially of about 0.1 to 0.75 weight percent ofplatinum and about 10 to 30 weight percent of aluminum chloride onactivated alumina.

8. The method of claim 7' wherein the first stage con ditions include apressure of about 400 to 1500 p.s.i.g.

and about 5 to 35% of a member selected from the group consisting ofamorphous hydrous alumina, alumina monohydrate and their mixture, andthe activated alumina has an area of about 350 to 500 square meters pergram.

10. The method of'claim 9 wherein the n-parafiin is pentane.

References (Iited in the file of this patent V UNITED STATES PATENTS2,349,516 Pines etal May 23, 1944 2,493,499 Perry Jan. 3, 1950 2,751,333Heinernann -June 19, 1956 FOREIGN PATENTS 555,861 Great Britain Sept. 9,1943

1. IN A METHOD FOR ISOMERIZING C5 TO C9 N-PARAFFINS IN A FEED CONTAININGAROMATICS, THE STEPS COMPRISING CONTACTING SAID N-PARAFFINS UNDER FIRSTSTAGE CONDITIONS WITH A FIRST STAGE CATALYST AT A TEMPERATURE OF ABOUT200 TO 750* F. AND IN THE PRESENCE OF FREE HYDROGEN TO PRODUCE A FIRSTSTAGE REACTION PRODUCT, CONTACTING THE FIRST STAGE REACTION PRODUCTUNDER SECOND STAGE CONDITIONS WITH A SECOND STAGE CATALYST AT ATEMPERATURE FROM ABOUT 150 TO 450*F. AND IN THE PRESENCE OF FREEHYDROGEN AND WHILE PROVIDING ABOUT 1 TO 25 PERCENT OF A HYDROGEN HALIDEWITH AN ATOMIC WEIGHT BETWEEN 35 AND 85 BASED ON THE FIRST STAGEREACTION PRODUCT, SAID FIRST STAGE CATALYST CONSISTING ESSENTIALLY OFABOUT 0.01 TO 2% OF PLATINUM GROUP NOBLE METAL AND ABOUT 3 TO 20% OFBORIA ON ACTIVATED ALUMINA AND SAID SECOND STAGE CATALYST CONSISTINGESSENTIALLY OF ABOUT 0.01 TO 2% OF A PLATINUM GROUP NOBLE METAL ANDABOUT 2 TO 50% OF AN ALUMINUM HALIDE FRIEDEL-CRAFTS COMPONENT ONACTIVATED ALUMINA.